The anthracenediones are a class of antineoplastic agents which have significant potential in the treatment of cancer. Mitoxantrone, an anthracenedione now in Phase II clinical trials, displays anti-tumor efficacy equal to or greater than that of Adriamycin with little systemic toxicity and no evidence of cardiotoxicity. The prototypic anthracenediones HAQ and mitoxantrone have been demonstrated via pharmacokinetic studies to undergo rapid accumulation to high concentration in the liver and significant hepatic metabolism. Little information is available, however, regarding the hepatic cytosolic or microsomal metabolism of HAQ or mitoxantrone or the effects of these drugs on the microsomal metabolism of other xenobiotics. Recent experiments in our laboratory using microsomes and purified NADPH-cytochrome P-450 reductase have revealed that HAQ inhibits normal electron transport and oxidative metabolism of xenobiotics in microsomes while undergoing little metabolic activation by flavoprotein reductase enzymes. Thus, the overall objectives of this research are to: (1) establish the nature and extent of hepatic cytosolic and microsomal metabolism of HAQ and mitoxantrone to include isolation and structural identification of major metabolites; (2) study the flavoprotein reductase-catalyzed activation of HAQ and mitoxantrone and the role of this process in metabolite formation (i.e. reduction followed by non-enzymic rearrangement); (3) determine the strength and type of HAQ or mitoxantrone inhibition of the microsomal metabolism of other xenobiotics; and (4) characterize the molecular basis of the interaction of HAQ or mitoxantrone with NADPH-cytochrome P-450 reductase to establish the site of inhibition. Techniques such as HPLC, H FT NMR spectroscopy and GC mass spectrometry will be used in the isolation and structural identification of the major metabolites and in molecular level studies. NADPH oxidation, superoxide or hydrogen peroxide formation, indicators of metabolism and metabolic activation, as well as xenobiotic metabolism will be monitored spectrophotometrically using standard assay procedures. Specific cofactors or enzyme inhibitors, in conjunction with enzyme induction will be used to implicate specific cytosolic or microsomal enzymes in the metabolism of HAQ and mitoxantrone. Information obtained from these studies will be of crucial importance in the clinical use and continued development of these drugs.